All - my motor has developed a loud tapping sound from the upper front of the motor in the vanos/valve cover area. Noise is audible from idle to about 4K when it blends into all the other engine noise. Most prominent at 1200-2000Rpms. I have removed the belt temporarily and noise persisits; this rules out the pullies, belt tensioner and bearings in the accessories. Car has ~30K miles. Valve shims were checked/passed at ~21K. Camshaft bolts were changed & threadlocked about 26K and valves where checked again. Engine is stock at the moment.

Likely causes include a noisy valve (lost shim?) or a vanos problem.

My question is: do I go with an unknown dealer with an admittedly good reputation - under warranty -- or do I use an independant BMW shop of known excellent quality and pay out of pocket? The worst-case scenario is probably a full vanos teardown/rebuild w/valve shims costing around a thousand-ish at the indy shop.

All - my motor has developed a loud tapping sound from the upper front of the motor in the vanos/valve cover area. Noise is audible from idle to about 4K when it blends into all the other engine noise. Most prominent at 1200-2000Rpms. I have removed the belt temporarily and noise persisits; this rules out the pullies, belt tensioner and bearings in the accessories. Car has ~30K miles. Valve shims were checked/passed at ~21K. Camshaft bolts were changed & threadlocked about 26K and valves where checked again.

Likely causes include a noisy valve (lost shim?) or a vanos problem.

My question is: do I go with an unknown dealer with an admittedly good reputation - under warranty -- or do I use an independant BMW shop of known excellent quality and pay out of pocket? The worst-case scenario is probably a full vanos teardown/rebuild w/valve shims costing around a thousand-ish at the indy shop.

I think you should try the dealer first if its under warranty, but given that your vehicle has been modified (not sure what mods you have) I'm pretty certain the dealer will claim you have voided your warranty and you'll have to pay out of pocket.

I think you should try the dealer first if its under warranty, but given that your vehicle has been modified (not sure what mods you have) I'm pretty certain the dealer will claim you have voided your warranty and you'll have to pay out of pocket.

I agree you should take it to the dealer first. You're car is modified, but it's not like you have a supercharger in there. The problem is engine related, and it'll be difficult for them to say your mods (most obvious is aftermarket springs? they probably won't even notice the gears) caused the vanos problem.

Of course go to the dealer if you are still under warranty. Why pay for something that could potentially be done for free?

Because the S54 is a very difficult engine to work on, and dealers have a tendency to mess up the timing. But I agree that you should try the dealership first. At the very least you'll be able to have a paper trail should a problem arise later post-warranty.

First seven days: dealer "couldn't hear the noise". Apparently they misunderstood the description of " a lound tapping noise from the top front of the motor" to mean a *high-pitched* tapping noise, which they indeed did not find as there was none. They gave the car back [!] and literally as I started it to leave, the familiar tak-tak-tak noise was cranking away. I didn't even move the car from the service lane. Instead I got my SA and the shop foreman to "inspect" the noise with me and they promptly agreeed that the medium-to-low pitched "tak-tak-tak" noise was not normal. Apparently they were content to send me on my way with the engine misbehaving because they couldn't find a 'high-pitched' tapping noise.

At my vigourously worded request, we re-opened the case on day 8 and actually began working on the problem. VANOS was inspected and appeared fine. I specifically requested that they inspect/torque the bolts on the intake & exhuast cam gears [sprockets].

Shortly thereafter, I got an emaiil saying " Found intake vanos bolts loose, should be done tomorrow and your request on the bolts will be done...DB"

It turns out that "both the intake and exhaust cam bolts were loose" and "some" were "broken". The shop foreman and mechanic were both in complete agreement that catastrophic failure was not far off and the service was absolutely required.

It took another 2.5 days to get the replacement bolts ordered and installed. [ why not stock them?? they are small & cheap!]

Car is running great once again, distaster averted. I can only guess what would have happened had I brought it home after the dealer's initial failure to diagnose/repair the problem-- highly likely that I would have been in line for a new S54B2 at their expense.

Incidentally, the dealer informed me that the national BMW service authorization desk in New Jersey knows about this problem but no TSB or SIB will be written. I suppose that would create too much expense, liability and culpability for BMW North America.

Anyway - next time you have the valves checked, check your cam bolts!! both sides!! and use threadlocker on them if you re-torque/replace any.

Another cam bolt case. Sheesh. But thanks for the heads up! Valve adjustment is due in 700 miles, so I will make sure this is throughly checked.

How many cases do we have on this board now? 10? 15? Out of a few hundred Z4M owners on this site? Not a good feeling.

If there's no problem found at the valve adjustment I think I'll just have the bolts replaced by my indie shop after the warranty expires next year. It's just cheap insurance to have them replaced on my dime as the alternative is uber costly.

Can someone specify exactly what needs to be done? There are multiple bolts which need checking/threadlocking/replacing correct? I think I will also have this done just as I had the engine mount bolts replaced. This issue could be very costly if it goes wrong. I also need to find a shop in Atlanta who is trustworthy enough to do the work.

I'm confused. I had thought that the fix for the Vanos/camshaft bolt issue that has been discussed here over the past few months involved special tools, turning the engine over by hand, etc. It appears from the pictures that what we are talking about in this thread is the simple removal and replacing (with loctite of course) of bolts. What am I missing here?

Having had an '04 M3 and spent lots of time on M3 Forum reading about this issue, I will say a few things to add to rclem05 has said so far.

BTW, rclem05 - please post mileage, just to add more data to the growing picture of this problem.

What I have gathered is that if there is any suspicion that these cam gear bolts are loose, they should be pulled and replaced, not re-torqued. It's somewhat unclear as to the exact cause of the problem, but the leading theory is that it's due to the bolts being incorrectly torqued at initial assembly.

Also, it seems as though BMW has recognized that there is a problem because the original bolts have already bee superseded with a new bolt that appears to have a form of loctite pre-placed on the bolts. It also kind of bugs me that they are being called VANOS bolts - these are specifically the cam gear bolts holding the cam gear to the cam shaft. You lose these bolts and you will have major valve and piston damage.

Because the S54 is normally a rather noisy engine, for lack of a better term, it seems like this rattle that comes from loose cam gear bolts might be hard to discern however, as rclem05 noticed, others have notices a new, lower pitch rattle that persists across rpm bands. From what I've gathered, the most important thing is to be in tune with the way your engine sounds as this is the best way to notice a change. If you notice a change in the way it sounds, time to get it looked at.

It seems that engines with a wide range of mileage on them are being affected. I've seen reports of cars with less than 20k miles being affected, and one guy with an M3 had this problem with over 90k miles.

It seems like a random problem that is not occurring with any particular cause or time frame - aggravating to say the least.

I'm confused. I had thought that the fix for the Vanos/camshaft bolt issue that has been discussed here over the past few months involved special tools, turning the engine over by hand, etc. It appears from the pictures that what we are talking about in this thread is the simple removal and replacing (with loctite of course) of bolts. What am I missing here?

You will want to review http://www.m3forum.net/m3forum/showthread.php?t=321494 - do not be misled, it is not easy and just the procedure to check can result in major valve train timing problems. This is precisely why even though BMW recognizes there is a problem, there will never be a TSB or recall. The problem, though potentially catastrophic, is rare and the cost to simply check the bolts is very high and requires techs with highly specialized understanding of how the S54, in specific, is timed.

The noise ---lower sounding tap/knock -- was obvious when it began.
I pulled the serpentine belt myself to rule out belt failure, accessories or tensioner. I did the rubber hose in the ear trick to isolate the sound to the top front of motor.

please can you decribe the sounds again "tak tak tak....? does it tak really fast? like 4 or more taks a second? do i have to pay close attention under the hood to realize? Thx for your posting.

At idle it was a medium-low pitched 'tak-tak-tak' about three or four cycles per second, that increases with idle speed, really obvious at around 1100 revs with hood open. You can hear it from the driver's seat if you park near a reflective wall.

I'm pretty sure you're NOT going to hear this on a E92 V8 though....can anyone comment?